In this talk we will review the several contributions to the pressure to the bubble wall assuming the relativistic regime, where particles can be taken as collisionless within the region of the wall. We will pay attention to leading and next-to-leading order contributions and study the effects of longitudinal modes, which undergo a discontinuity across the step wall, within the formalism of...
In this talk, I will discuss a supercooled phase transition present in a model with classical conformal symmetry. I will review the details of the model and the predictions for the properties of the phase transition, dark matter, and resulting gravitational-wave spectra paying special attention to the behaviour of the bubble walls. Using this exemplary model I will aim to summarize the state...
In this talk we will present a novel mechanism for baryogenesis relying on ultra relativistic bubble walls during a first order phase transition. The baryon asymmetry is sourced by the CP and baryon-number violating decay of heavy and out-of-equilibrium states which are produced as a result of high-energy particle-wall collisions. We illustrate two different realizations based on 1) light...
In this talk, we demonstrate how to predict the gravitational wave spectra of Strongly coupled QFTs using holography and lattice data input for a pure SU(3) Yang-Mills theory with minor uncertainties. We will elaborate on how we obtain an effective potential using holography with the free energy landscape approach and formulate an effective action. Once the effective action is in our grasp, we...
In bubble wall friction calculations, a singularity is found in the fluctuations as the wall approaches the speed of sound. We argue that a discontinuity across the speed of sound is expected on general grounds, which manifests itself as the singularity in the solution of the linearized system.
In the first part of this talk, I will derive the fluid equations needed to compute the wall velocity from first principles. By treating the background and out-of-equilibrium perturbations in a consistent way, the resulting equations are free of the discontinuity at v_w=c_s that was observed in previous studies. I will show that the solutions can naturally be classified as deflagration/hybrid...
Bubble nucleation is a key aspect of a cosmological first-order phase transition. The non-equilibrium bubble dynamics and the properties of the transition are controlled by the density perturbations in the hot plasma. We present a new spectral method devised for a fast and reliable computation of the collision integral in the Boltzmann equations. In a scalar singlet extension of the Standard...
Terminal velocity reached by bubble walls in first order phase
transitions is an important parameter determining both primordial gravitational-wave spectrum and production of baryon asymmetry in models of electroweak baryogenesis. We developed a numerical code to study real-time evolution of expanding bubbles and investigated how
their walls reach stationary states. Our results agree with...
In first-order cosmological phase transitions, it is commonly accepted that subluminal bubble expansion requires out-of-equilibrium interactions with the plasma which are captured by friction terms in the equations of motion for the scalar field. This has been disputed in works pointing out subluminal velocities in local equilibrium arising either from hydrodynamic effects in deflagrations or...
It is commonly expected that a friction force on the bubble wall can only arise from out-of-equilibrium effects. In this talk, I will discuss the bubble wall motion in local thermal equilibrium. We show that there is a nonvanishing effective friction on the wall in local thermal equilibrium provided that the plasma temperature distribution is inhomogeneous across the wall. Further, we propose...
In the study of the equilibrium properties of high-temperature phase
transitions, effective field theories have been extremely fruitful. On
the one hand, they make possible nonperturbative lattice simulations,
which yield unambiguously reliable results up to small statistical
uncertainties. On the other hand, by knitting together chains of
effective field theories, perturbative...
Together with the bubble wall velocity, uncertainties of the thermodynamic parameters of the electroweak phase transition can still be large and are subject to the finite-temperature scale hierarchy of gauge theories. While massless gauge bosons are rendered non-perturbative in the infrared, scalar bosons face slow perturbative convergence.
To reliably describe the phase transition...
A limiting factor in accurately determining the gravitational wave spectrum from an underlying microphysical model, in addition to the wall speed, is the nucleation rate. I will discuss recent progresses in computing nucleation rates reliably, in particular a high-temperature effective field theory framework. At high-temperatures, there is a well-known hierarchy between the thermal particles...
A first order cosmological phase transition can give rise to very interesting phenomenology such as gravitational waves, generation of the matter-antimatter asymmetry. These processes depend sensitively on the parameters of the phase transition. Of these parameters, the velocity with which the bubble wall expands has been the most elusive. In this three-day conference, we get an overview of...
